B4 SOUTH AFRICAN BOTANY 
it round the basal part of the root a large quantity of 
soil particles, while the tip of the root comes out clean 
and bare (fig. 19). The root-hairs are only short-lived 
organs, dying away as the root grows older. 
21. The Tissues of the Root.—If we cut across a 
young root of a bean or sunflower we can make out a 
number of specks arranged in a ring. 
These specks are the vascular bundles 
which run longitudinally through the 
root conveying liquids to and from its 
different parts. On the outside of this 
ring of bundles is a mass of tissue called 
the cortex. The outermost layer of 
this tissue is called the PILIFEROUS 
Layer. Inside the ring of vascular 
bundles is a mass of tissue very much 
resembling the cortex. It is known as 
the pith. 
22. Microscopic Structure of Root.—If 
the section be examined a little more 
ie Rae closely it will be noticed that it consists 
with Soil Ad- of a central cylinder surrounded by the 
hering to Root- : ; 
hairs (after cortex (fig. 20). The innermost layer of 
Beehs). the cortex is known as the endodermis, 
or bundle sheath. The vascular‘ tissue is seen to be 
of two kinds placed alternately with one another ina 
ring. The larger, thick-walled, empty cells make up the 
xylem, or wood; the smaller, living, thin-walled cells, 
the phloem. In the bean there are usually five xylem 
groups and five phloem groups. The largest xylem cell 
walls are no longer made of cellulose, but of a trans- 
